JP2018207064A - Piezoelectric element, and device as application thereof - Google Patents

Abstract

To provide: a piezoelectric element which has a KNN-based piezoelectric material layer and is superior in leak characteristic; and a device as an application of the piezoelectric element.SOLUTION: A piezoelectric element 300 comprises: a first electrode 60; a second electrode 80; and a piezoelectric material layer 70 provided between the first electrode 60 and the second electrode 80, and made of a perovskite oxide including at least one selected from a group consisting of potassium, sodium and niobium. The piezoelectric element further comprises: a first perovskite layer 171 provided between the piezoelectric material layer 70 and the first electrode 60, and made of a perovskite oxide different, in composition, from the piezoelectric material layer 70; and a second perovskite layer 172 provided between the piezoelectric material layer 70 and the second electrode 80, and made of a perovskite oxide different, in composition, from the piezoelectric material layer 70.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a piezoelectric element including a first electrode, a piezoelectric layer, and a second electrode, and a piezoelectric element application device including the piezoelectric element.

  A piezoelectric element generally has a piezoelectric layer having electromechanical conversion characteristics and two electrodes that sandwich the piezoelectric layer. In recent years, development of devices using such piezoelectric elements as drive sources (piezoelectric element applied devices) has been actively conducted. As one of piezoelectric device application devices, a liquid jet head typified by an ink jet recording head, a MEMS element typified by a piezoelectric MEMS element, an ultrasonic measuring device typified by an ultrasonic sensor, and a piezoelectric actuator device Etc.

  As a material (piezoelectric material) of a piezoelectric layer of a piezoelectric element, lead zirconate titanate (PZT) is known. However, from the viewpoint of environmental problems, there is a demand for a piezoelectric material with reduced lead or lead content. As a piezoelectric material not containing lead, for example, there is a potassium sodium niobate (KNN) type piezoelectric material containing K, Na and Nb. The KNN-based material has a problem that a leak current is generated. However, a technique for taking insulation measures by adding a rare earth element has been proposed (see Patent Document 1).

JP 2013-225605 A

  However, depending on the additive and its amount, there are problems such as random orientation without crystal orientation and the appearance of heterogeneous phases, ensuring insulation while maintaining orientation without the occurrence of heterogeneous phases. It is difficult to do.

  Such problems are not limited to piezoelectric elements used in piezoelectric actuators mounted on liquid jet heads typified by ink jet recording heads, and exist similarly in piezoelectric elements used in other piezoelectric element application devices. To do.

  In view of such circumstances, an object of the present invention is to provide a piezoelectric element having a KNN piezoelectric layer and having excellent leakage characteristics, and a piezoelectric element application device.

  An aspect of the present invention that solves the above-described problems is a first electrode, a second electrode, potassium provided between the first electrode and the second electrode, sodium, bismuth, and niobium. A piezoelectric layer comprising a perovskite oxide containing at least one selected from the piezoelectric layer, the piezoelectric layer provided between the piezoelectric layer and the first electrode side; Is a first perovskite oxide composed of a perovskite oxide having a different composition, and a first perovskite oxide composed of a perovskite oxide having a composition different from that of the piezoelectric layer provided between the piezoelectric layer and the second electrode. A piezoelectric element comprising a two perovskite layer.

  In this aspect, the piezoelectric layer made of a perovskite oxide containing at least one selected from the group consisting of potassium, sodium, bismuth, and niobium is formed from a perovskite oxide having a composition different from that of the piezoelectric layer. By adopting a configuration in which the first perovskite layer and the second perovskite layer are sandwiched, the leakage characteristics are excellent.

  Here, it is preferable that the first perovskite layer and the second perovskite layer include at least one selected from the group consisting of bismuth and iron. According to this, the first perovskite layer and the second perovskite layer comprising at least one selected from the group consisting of bismuth and iron are selected from the group consisting of potassium, sodium, bismuth and niobium. By adopting a structure in which a piezoelectric layer made of a perovskite oxide containing at least one of the above is sandwiched, leakage characteristics are excellent.

  The piezoelectric layer is preferably preferentially oriented in the (100) plane. According to this, a piezoelectric layer having particularly excellent piezoelectric characteristics is obtained.

  The first perovskite layer is preferably made of a perovskite oxide containing bismuth or iron and preferentially oriented in the (100) plane. According to this, the piezoelectric layer can be oriented in the (100) plane relatively easily.

  Preferably, an orientation control layer is provided between the first electrode and the first perovskite layer or between the first perovskite layer and the piezoelectric layer. According to this, the piezoelectric layer can be oriented in the (100) plane relatively easily.

  The second perovskite layer is preferably made of a perovskite oxide containing bismuth or iron and preferentially oriented in the (100) plane. According to this, a piezoelectric element having particularly excellent piezoelectric characteristics is obtained.

  Each of the first perovskite layer and the second perovskite layer is preferably thinner than the piezoelectric layer. Thereby, a piezoelectric element having superior piezoelectric characteristics can be realized.

  The first electrode and the second electrode may be selected from at least one material selected from Pt, Ir, and oxides thereof. Thereby, a piezoelectric element having superior piezoelectric characteristics can be realized.

  Moreover, it is preferable that a layer made of zirconium or zirconium oxide is provided between the substrate on which the first electrode is provided and the first electrode. According to this, permeation of the alkali metal into the substrate can be prevented, and a piezoelectric element having superior piezoelectric characteristics can be realized.

Furthermore, another aspect of the present invention is a piezoelectric element application device comprising the above piezoelectric element.
In this aspect, a piezoelectric element application device having excellent leakage characteristics can be realized.

1 is a diagram illustrating a schematic configuration of a recording apparatus. FIG. 3 is an exploded perspective view of a recording head. FIG. 2 is a plan view of a recording head. FIG. 3 is a cross-sectional view of a recording head. It is sectional drawing which shows the manufacturing method of a recording head. It is sectional drawing which shows the manufacturing method of a recording head. It is sectional drawing which shows the manufacturing method of a recording head. It is sectional drawing which shows the manufacturing method of a recording head. It is sectional drawing which shows the manufacturing method of a recording head. It is sectional drawing which shows the manufacturing method of a recording head. It is sectional drawing which shows the manufacturing method of a recording head. It is a figure which shows the hysteresis curve of Example 1. FIG. It is a figure which shows the hysteresis curve of the comparative example 1. FIG. 2 is a diagram showing XRD of Example 1. FIG. FIG. 4 is a diagram showing an XRD of Example 2.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the following description shows one embodiment of the present invention, and can be arbitrarily changed within the scope of the present invention. In the drawings, the same reference numerals denote the same members, and descriptions thereof are omitted as appropriate. 2 to 11, X, Y, and Z represent three spatial axes that are orthogonal to each other. In this specification, directions along these axes will be described as an X direction, a Y direction, and a Z direction, respectively. The Z direction represents the thickness direction or the stacking direction of the plates, layers, and films. The X direction and the Y direction represent in-plane directions of the plate, layer, and film.

(Embodiment 1)
FIG. 1 is an ink jet recording apparatus which is an example of a liquid ejecting apparatus including a recording head which is an example of a piezoelectric element application device according to an embodiment of the present invention. As shown in the drawing, in an ink jet recording apparatus I, an ink jet recording head unit (head unit) II having a plurality of ink jet recording heads is detachably provided with cartridges 2A and 2B constituting ink supply means. . The carriage 3 on which the head unit II is mounted is provided on a carriage shaft 5 attached to the apparatus main body 4 so as to be movable in the axial direction, and for example, ejects a black ink composition and a color ink composition, respectively. .

  Then, the driving force of the driving motor 6 is transmitted to the carriage 3 through a plurality of gears and a timing belt 7 (not shown), so that the carriage 3 on which the head unit II is mounted is moved along the carriage shaft 5. On the other hand, the apparatus main body 4 is provided with a conveyance roller 8 as a conveyance means, and a recording sheet S which is a recording medium such as paper is conveyed by the conveyance roller 8. The conveying means for conveying the recording sheet S is not limited to the conveying roller, and may be a belt, a drum, or the like.

  Such an ink jet recording apparatus I includes an ink jet recording head (hereinafter also simply referred to as “recording head”), and therefore can be manufactured at low cost. Moreover, since the improvement of the displacement characteristic of the piezoelectric element constituting the piezoelectric actuator is also expected, the injection characteristic can be improved.

  An example of the recording head 1 mounted on the ink jet recording apparatus I described above will be described with reference to FIGS. FIG. 2 is an exploded perspective view of a recording head that is an example of a liquid jet head according to the present embodiment. FIG. 3 is a plan view of the flow path forming substrate on the piezoelectric element side, and FIG. 4 is a cross-sectional view corresponding to the line AA ′ of FIG.

  The flow path forming substrate 10 (hereinafter referred to as “substrate 10”) is made of, for example, a silicon single crystal substrate, and has a pressure generating chamber 12 formed therein. The pressure generating chambers 12 partitioned by the plurality of partition walls 11 are provided with a plurality of nozzle openings 21 that discharge the same color ink along the X direction.

  An ink supply path 13 and a communication path 14 are formed on one end side in the Y direction of the pressure generation chamber 12 in the substrate 10. The ink supply path 13 is configured so that one side of the pressure generation chamber 12 is narrowed from the X direction so that the opening area thereof is reduced. The communication passage 14 has substantially the same width as the pressure generation chamber 12 in the X direction. A communication portion 15 is formed on the outside (+ Y direction side) of the communication path 14. The communication part 15 constitutes a part of the manifold 100. The manifold 100 serves as an ink chamber common to the pressure generation chambers 12. As described above, the substrate 10 is formed with a liquid flow path including the pressure generation chamber 12, the ink supply path 13, the communication path 14, and the communication portion 15.

  On one surface (surface on the −Z direction side) of the substrate 10, for example, a SUS nozzle plate 20 is bonded. Nozzle openings 21 are arranged in the nozzle plate 20 along the X direction. The nozzle opening 21 communicates with each pressure generation chamber 12. The nozzle plate 20 can be bonded to the substrate 10 with an adhesive, a heat welding film, or the like.

A diaphragm 50 is formed on the other surface (the surface on the + Z direction side) of the substrate 10. The diaphragm 50 is constituted by, for example, an elastic film 51 formed on the substrate 10 and an insulator film 52 formed on the elastic film 51. The elastic film 51 is made of, for example, silicon dioxide (SiO ₂ ), and the insulator film 52 is made of, for example, zirconium oxide (ZrO ₂ ). The elastic film 51 may not be a separate member from the substrate 10. A part of the substrate 10 may be processed to be thin and used as an elastic film.

On the insulator film 52, the piezoelectric element 300 including the first electrode 60, the piezoelectric layer 70, and the second electrode 80 is formed via the adhesion layer 56. The adhesion layer 56 is for improving the adhesion between the first electrode 60 and the base. Examples of the adhesion layer 56 include titanium oxide (TiO _x ), titanium (Ti), or silicon nitride (SiN). ) Etc. can be used. Note that the adhesion layer 56 can be omitted. In addition, an orientation control layer (also referred to as a seed layer) for controlling the orientation of the piezoelectric layer 70 may be provided on the adhesion layer 56 or in a configuration in which the adhesion layer 56 is omitted.

  In the present embodiment, the diaphragm 50 and the first electrode 60 are displaced by the displacement of the piezoelectric layer 70 having electromechanical conversion characteristics. That is, in the present embodiment, the diaphragm 50 and the first electrode 60 substantially have a function as a diaphragm. The elastic film 51 and the insulator film 52 may be omitted, and only the first electrode 60 may function as a diaphragm. When the first electrode 60 is directly provided on the substrate 10, it is preferable to protect the first electrode 60 with an insulating protective film or the like so that ink does not contact the first electrode 60.

  The piezoelectric layer 70 is provided between the first electrode 60 and the second electrode 80. The piezoelectric layer 70 is formed with a width wider than that of the first electrode 60 in the X direction. Further, the piezoelectric layer 70 is formed with a width wider than the length of the pressure generation chamber 12 in the Y direction in the Y direction. In the Y direction, the end of the piezoelectric layer 70 on the ink supply path 13 side (the end in the + Y direction) is formed to the outside of the end of the first electrode 60. That is, the other end (the end on the + Y direction side) of the first electrode 60 is covered with the piezoelectric layer 70. On the other hand, one end portion (end portion on the −Y direction side) of the piezoelectric layer 70 is on the inner side than one end portion (end portion on the −Y direction side) of the first electrode 60. That is, one end portion (end portion on the −Y direction side) of the first electrode 60 is not covered with the piezoelectric layer 70.

  The second electrode 80 is continuously provided on the piezoelectric layer 70, the first electrode 60, and the diaphragm 50 in the X direction. That is, the second electrode 80 is configured as a common electrode common to the plurality of piezoelectric layers 70. Instead of the second electrode 80, the first electrode 60 may be a common electrode.

  A protective substrate 30 is bonded to the substrate 10 on which the piezoelectric element 300 is formed by an adhesive 35. The protective substrate 30 has a manifold portion 32. The manifold part 32 constitutes at least a part of the manifold 100. The manifold portion 32 according to the present embodiment penetrates the protective substrate 30 in the thickness direction (Z direction), and is further formed across the width direction (X direction) of the pressure generating chamber 12. The manifold portion 32 communicates with the communication portion 15 of the substrate 10 as described above. With these configurations, the manifold 100 serving as an ink chamber common to the pressure generation chambers 12 is configured.

  On the protective substrate 30, a piezoelectric element holding portion 31 is formed in a region including the piezoelectric element 300. The piezoelectric element holding portion 31 has a space that does not hinder the movement of the piezoelectric element 300. This space may or may not be sealed. The protective substrate 30 is provided with a through hole 33 that penetrates the protective substrate 30 in the thickness direction (Z direction). The end portion of the lead electrode 90 is exposed in the through hole 33.

  A drive circuit 120 that functions as a signal processing unit is fixed on the protective substrate 30. As the drive circuit 120, for example, a circuit board or a semiconductor integrated circuit (IC) can be used. The drive circuit 120 and the lead electrode 90 are electrically connected via the connection wiring 121. The drive circuit 120 can be electrically connected to the printer controller 200. Such a drive circuit 120 functions as a control unit according to the present embodiment.

  A compliance substrate 40 including a sealing film 41 and a fixing plate 42 is bonded onto the protective substrate 30. A region of the fixing plate 42 facing the manifold 100 is an opening 43 that is completely removed in the thickness direction (Z direction). One surface (the surface on the + Z direction side) of the manifold 100 is sealed only with a flexible sealing film 41.

  Next, details of the piezoelectric element 300 will be described. The piezoelectric element 300 includes a first electrode 60, a second electrode 80, and a piezoelectric layer 70 provided between the first electrode 60 and the second electrode 80. The thickness of the first electrode 60 is about 50 nm. The piezoelectric layer 70 is a so-called thin film piezoelectric body having a thickness of 50 nm to 2000 nm. The thickness of the second electrode 80 is about 50 nm. The thickness of each element listed here is an example, and can be changed within a range not changing the gist of the present invention.

  The material of the first electrode 60 and the second electrode 80 is preferably a noble metal such as platinum (Pt) or iridium (Ir) or an oxide thereof. The material of the 1st electrode 60 and the material of the 2nd electrode 80 should just be a material which has electroconductivity. The material of the first electrode 60 and the material of the second electrode 80 may be the same or different.

The piezoelectric layer 70 is formed of a thin film as described above, and is formed by a solution method (also referred to as a liquid phase method or a wet method) such as a MOD method or a sol-gel method, or a vapor phase method such as a sputtering method. . In this embodiment, it is a perovskite type oxide represented by the general formula ABO ₃ formed by a solution method and containing potassium (K), sodium (Na), and niobium (Nb).

The piezoelectric layer 70 is made of a complex oxide having a perovskite structure represented by a general formula ABO ₃ containing potassium (K), sodium (Na), and niobium (Nb). That is, the piezoelectric layer 70 includes a piezoelectric material made of a KNN-based complex oxide represented by the following formula (1).

(K _X , Na _1-X ) NbO ₃ (1)
(0.1 ≦ X ≦ 0.9)

The complex oxide represented by the above formula (1) is a so-called KNN-based complex oxide. Since the KNN-based composite oxide is a lead-free piezoelectric material with a reduced content of lead (Pb) or the like, it is excellent in biocompatibility and has little environmental impact. In addition, KNN-based composite oxides are advantageous in improving various characteristics because they are excellent in piezoelectric characteristics among lead-free piezoelectric materials. In addition, the KNN-based composite oxide may contain other lead-free piezoelectric materials (for example, BNT-BKT-BT; [(Bi, Na) TiO ₃ ]-[(Bi, K) TiO ₃ ]-[BaTiO ₃ ], The Curie temperature is relatively high, and depolarization due to temperature rise hardly occurs, so that it can be used at high temperatures.

  In the above formula (1), the content of K is 30 mol% or more and 70 mol% or less with respect to the total amount of metal elements constituting the A site (in other words, the content of Na constitutes the A site. It is preferably 30 mol% or more and 70 mol% or less with respect to the total amount of metal elements). That is, in the above formula (1), it is preferable that 0.3 ≦ x ≦ 0.7. According to this, a composite oxide having a composition advantageous in piezoelectric characteristics is obtained. The K content is 40 mol% or more and 60 mol% or less with respect to the total amount of metal elements constituting the A site (in other words, the Na content is equal to the total amount of metal elements constituting the A site. It is more preferably 40 mol% or more and 60 mol% or less. That is, in the above formula (1), it is more preferable that 0.4 ≦ x ≦ 0.6. According to this, a composite oxide having a composition more advantageous for piezoelectric characteristics is obtained.

  The piezoelectric material constituting the piezoelectric layer 70 may be a KNN-based composite oxide, and is not limited to the composition represented by the above formula (1). For example, other metal elements (additives) may be contained in the A site and B site of potassium sodium niobate. Examples of such additives include manganese (Mn), lithium (Li), barium (Ba), calcium (Ca), strontium (Sr), zirconium (Zr), titanium (Ti), bismuth (Bi), Examples include tantalum (Ta), antimony (Sb), iron (Fe), cobalt (Co), silver (Ag), magnesium (Mg), zinc (Zn), and copper (Cu).

One or more additives of this type may be included. In general, the amount of the additive is 20% or less, preferably 15% or less, more preferably 10% or less, based on the total amount of elements as the main component. The use of additives makes it easy to diversify the structure and functions by improving various characteristics. However, the presence of more than 80% of KNN is preferable from the viewpoint of exhibiting characteristics derived from KNN. Even when a composite oxide containing these other elements, is preferably configured to have a ABO ₃ type perovskite structure.

  The A-site alkali metal may be added in excess relative to the stoichiometric composition. Further, the alkali metal at the A site may be insufficient with respect to the stoichiometric composition. Therefore, the composite oxide of this embodiment can also be expressed by the following formula (2). In the following formula (2), A represents the amount of K and Na that may be added in excess or the amount of K and Na that may be insufficient. When the amount of K and Na is excessive, 1.0 <A. If the amount of K and Na is insufficient, A <1.0. For example, if A = 1.1, when the amount of K and Na in the stoichiometric composition is 100 mol%, it represents that 110 mol% of K and Na are contained. If A = 0.9, it means that 90 mol% of K and Na are contained when the amount of K and Na in the stoichiometric composition is 100 mol%. When the alkali metal at the A site is neither excessive nor insufficient with respect to the stoichiometric composition, A = 1. From the viewpoint of improving characteristics, 0.85 ≦ A ≦ 1.20, preferably 0.90 ≦ A ≦ 1.15, and more preferably 0.95 ≦ A ≦ 1.10.

(K _AX , Na _{A (1-X)} ) NbO ₃ (2)
(0.1 ≦ x ≦ 0.9, preferably 0.3 ≦ x ≦ 0.7, more preferably 0.4 ≦ x ≦ 0.6)

  The piezoelectric material includes a material having a composition in which a part of the element is deficient, a material having a composition in which part of the element is excessive, and a material having a composition in which a part of the element is replaced with another element. As long as the basic characteristics of the piezoelectric layer 70 do not change, materials that deviate from the stoichiometric composition due to defects or excess, or materials in which some of the elements are replaced with other elements are also applicable to the piezoelectric according to the present embodiment. Included in the material.

Further, in the present specification, "K, composite oxides of ABO ₃ type perovskite structure containing Na and Nb" is, K, is not limited only to the composite oxide ABO ₃ type perovskite structure containing Na and Nb. KNN i.e., "K, composite oxides of ABO ₃ type perovskite structure containing Na and Nb," as used herein, K, composite oxides of ABO ₃ type perovskite structure containing Na and Nb (e.g., illustrated above And a piezoelectric material represented as a mixed crystal including an ABO ₃ type perovskite structure.

  Other complex oxides are not limited within the scope of the present invention, but are preferably lead-free piezoelectric materials that do not contain lead (Pb). The other composite oxide is more preferably a lead-free piezoelectric material that does not contain lead (Pb) and bismuth (Bi). According to these, the piezoelectric element 300 is excellent in biocompatibility and has little environmental load.

  In the present embodiment, the piezoelectric layer 70 made of the complex oxide as described above is crystal-oriented in the {100} direction, that is, preferentially oriented with respect to the (100) crystal plane. In the present embodiment, the layer is preferentially oriented to the (100) plane, and the layer preferentially oriented to the (100) plane is preferable in terms of piezoelectric characteristics. Note that in this specification, the preferential orientation indicates that 50% or more, preferably 80% or more of the crystals are oriented in a predetermined crystal plane. For example, “preferentially oriented in the (100) plane” means that all the crystals of the piezoelectric layer 70 are oriented in the (100) plane and more than half of the crystals (50% or more, preferably 80%). Includes the case of being oriented in the (100) plane.

  A first perovskite layer 171 is provided between the piezoelectric layer 70 and the first electrode 60, and a second perovskite layer 172 is provided between the piezoelectric layer 70 and the second electrode 80. Yes.

  Here, the first perovskite layer 171 and the second perovskite layer 172 are made of a perovskite oxide including at least one selected from the group consisting of bismuth and iron, and the first perovskite layer 171 and the second perovskite layer 171. The same material may be sufficient as 172, and a different material may be sufficient as it.

  The perovskite oxide containing at least one selected from the group consisting of bismuth and iron contains bismuth as the A site element and at least selected from iron, cobalt, nickel, manganese, zinc, titanium, etc. as the B site element. A perovskite oxide containing one kind, or a perovskite oxide containing at least one kind selected from bismuth, lanthanum, cerium, praseodymium, neodymium, samarium, europium, and the like as an A site element and iron as a B site element The In particular, a perovskite oxide containing bismuth as the A site element and iron as the B site element, that is, a BFO-based perovskite oxide is preferable.

  Since the first perovskite layer 171 and the second perovskite layer 172 have the above-described composition, the leakage characteristics of the piezoelectric layer 70 can be improved as will be described in detail later. Considering only the improvement of leak characteristics, BFO-based perovskite oxide is preferable. The first perovskite layer 171 and the second perovskite layer 172 do not necessarily have piezoelectric characteristics, but perovskite oxides having piezoelectric characteristics are preferable.

  The first perovskite layer 171 and the second perovskite layer 172 have a thickness of 5 nm or more, preferably 10 nm or more, and more preferably 20 nm or more for the purpose of improving leakage characteristics. On the other hand, the first perovskite layer 171 and the second perovskite layer 172 are preferably as thin as possible because they contribute to a substantial decrease in the piezoelectric characteristics of the piezoelectric element 300, particularly when the dielectric constant is low. It is preferable that each of them is at least thinner than the piezoelectric layer 70, and the difference sum is preferably thinner than the piezoelectric layer 70. Specifically, the thickness is preferably 100 nm or less, preferably 70 nm or less, more preferably 50 nm or less.

  In addition, the first perovskite layer 171 and the second perovskite layer 172, particularly the first perovskite layer 171 serving as the underlayer of the piezoelectric layer 70, is preferably preferentially oriented in the (100) plane. This is because it is preferable for preferentially orienting the piezoelectric layer 70 in the (100) plane.

  When the first perovskite layer 171 is difficult to self-orient in the (100) plane, an orientation control layer is provided on the base of the first perovskite layer 171, and the first perovskite layer 171 is (100) by orientation control by the orientation control layer. You may make it preferentially orientate to a surface.

  As such an orientation control layer, for example, it has a perovskite structure, the A site contains bismuth (Bi), the B site contains iron (Fe) and titanium (Ti), and is self-oriented in the (100) plane. And the composite oxide.

  Further, an orientation control layer may be provided between the first perovskite layer 171 and the piezoelectric layer 70, and the piezoelectric layer 70 may be preferentially oriented in the (100) plane by orientation control by the orientation control layer.

  As such an orientation control layer, the orientation control layer 73 includes potassium (K), sodium (Na), calcium (Ca), and niobium (Nb), and has a perovskite structure preferentially oriented in the (100) plane. The thing containing the crystal | crystallization of complex oxide (perovskite type complex oxide) can be mentioned. This perovskite complex oxide is composed of a complex oxide (referred to as “kncn”) in which the A site contains K, Na, and Ca, and the B site contains Nb. It functions as an orientation control layer that preferentially orients in the (100) plane and preferentially orients the piezoelectric layer 70 having a perovskite structure formed thereon on the (100) plane.

  Further, an orientation control layer or an orientation control layer and an adhesion layer are provided on the base layer of the first electrode 60, and the first electrode 60 is preferentially oriented on the (100) plane, whereby the first perovskite layer 171 is (100). You may make it carry out priority orientation to a surface.

  As such an orientation control layer, for example, it is composed of a composite oxide containing at least one selected from bismuth, manganese, iron and titanium, preferably bismuth and manganese, or bismuth, manganese and iron, or bismuth, iron. And a composite oxide containing titanium. By providing such an orientation control layer, the first electrode 60 formed thereon can be preferentially oriented in the (100) plane. Preferably, an adhesion layer is provided between the orientation control layer and the first electrode 60, the orientation control layer preferentially orients the adhesion layer on the (100) plane, and the first electrode 60 is (100) through the adhesion layer. ) May be preferentially oriented in the plane.

  Examples of such an adhesion layer include those composed of at least one complex oxide selected from bismuth, manganese, iron, and titanium, the orientation of which is controlled by the orientation control layer. When the adhesion layer has a perovskite structure, the matching property between the metal (first electrode 60) formed thereon and the lattice constant is improved, and the adhesion between the diaphragm and the first electrode 60 is improved.

  The thicknesses of the various orientation control layers described above may be any thickness as long as the layers formed thereon can be preferentially oriented in the (100) plane, and are preferably 5 nm to 40 nm. Is 5 nm to 15 nm. The orientation control layer having such a thickness may be provided in an island shape, for example. “Island” refers to a state in which a plurality of crystal grains are formed apart from each other.

  Next, an example of a method for manufacturing the piezoelectric element 300 will be described together with a method for manufacturing the ink jet recording head 1 with reference to FIGS. First, a silicon substrate (hereinafter also referred to as “wafer”) 110 is prepared. Next, the silicon substrate 110 is thermally oxidized to form an elastic film 51 made of silicon dioxide on the surface thereof. Further, a zirconium film is formed on the elastic film 51 by a sputtering method, and the insulator film 52 is formed by thermally oxidizing the zirconium film. In this way, the diaphragm 50 composed of the elastic film 51 and the insulator film 52 is obtained. Next, an adhesion layer 56 made of titanium oxide is formed on the insulator film 52 by sputtering, thermal oxidation of the titanium film, or the like. Then, as shown in FIG. 5, the first electrode 60 is formed on the adhesion layer 56 by a sputtering method, a vapor deposition method, or the like.

  Next, as shown in FIG. 6, a resist (not shown) having a predetermined shape is formed on the first electrode 60 as a mask, and the adhesion layer 56 and the first electrode 60 are patterned simultaneously. Next, as shown in FIG. 7, a plurality of first perovskite layers 171 and piezoelectric films 74 are formed so as to overlap the adhesion layer 56, the first electrode 60, and the diaphragm 50. In addition, a second perovskite layer 172 is formed. The piezoelectric layer 70 is composed of these multiple layers of piezoelectric films 74. Each of the first perovskite layer 171 and the second perovskite layer 172 is also composed of a plurality of layers. The piezoelectric layer 70, the first perovskite layer 171 and the second perovskite layer 172 can be formed by a solution method (chemical solution method) such as a MOD method or a sol-gel method, for example. Thus, by forming the piezoelectric layer 70, the first perovskite layer 171 and the second perovskite layer 172 by the solution method, the productivity of the piezoelectric layer 70 can be increased. The piezoelectric layer 70 thus formed by the solution method is formed by repeating a series of steps from the step of applying the precursor solution (application step) to the step of baking the precursor film (firing step) a plurality of times. Is done.

  A specific procedure for forming the piezoelectric layer 70, the first perovskite layer 171 and the second perovskite layer 172 by a solution method is, for example, as follows. First, a precursor solution containing a predetermined metal complex is prepared. The precursor solution of the piezoelectric layer 70 is obtained by dissolving or dispersing a metal complex capable of forming a composite oxide containing K, Na, and Nb in an organic solvent by firing. At this time, a metal complex containing an additive such as Mn may be further mixed.

  Examples of the metal complex containing K include potassium 2-ethylhexanoate and potassium acetate. Examples of the metal complex containing Na include sodium 2-ethylhexanoate and sodium acetate. Examples of the metal complex containing Nb include niobium 2-ethylhexanoate and pentaethoxyniobium. When Mn is added as an additive, examples of the metal complex containing Mn include manganese 2-ethylhexanoate. At this time, two or more metal complexes may be used in combination. For example, potassium 2-ethylhexanoate and potassium acetate may be used in combination as a metal complex containing K. Examples of the solvent include 2-n butoxyethanol, n-octane, or a mixed solvent thereof. The precursor solution may include an additive that stabilizes the dispersion of the metal complex containing K, Na, and Nb. Examples of such additives include 2-ethylhexanoic acid.

  The precursor solution of the first perovskite layer 171 and the second perovskite layer 172 is mixed with a metal complex capable of forming the composite oxide layers 173 and 174 containing Bi and Fe by firing, and the mixture is dissolved in an organic solvent. Or they are dispersed. As a metal complex containing Bi and Fe, for example, alkoxide, organic acid salt, β-diketone complex, and the like can be used. Examples of the metal complex containing Bi include bismuth 2-ethylhexanoate and bismuth acetate. Examples of the metal complex containing Fe include iron 2-ethylhexanoate, iron acetate, and tris (acetylacetonato) iron. Examples of the solvent for the precursor solution include propanol, butanol, pentanol, hexanol, octanol, ethylene glycol, propylene glycol, octane, decane, cyclohexane, xylene, toluene, tetrahydrofuran, acetic acid, octylic acid, and the like.

  And said precursor solution is apply | coated on the wafer 110 in which the diaphragm 50, the contact | adherence layer 56, and the 1st electrode 60 were formed, and a precursor film | membrane is formed (application | coating process). Next, the precursor film is heated to a predetermined temperature, for example, about 130 ° C. to 250 ° C., and dried for a predetermined time (drying step). Next, the dried precursor film is degreased by heating to a predetermined temperature, for example, 300 ° C. to 450 ° C., and holding at this temperature for a certain period of time (degreasing step). Finally, when the degreased precursor film is crystallized by heating to a higher temperature, for example, about 600 ° C. to 800 ° C. and holding at this temperature for a certain time, the composite oxide layer 173, the piezoelectric film 74 and the composite film The oxide layer 174 is completed (firing process). Moreover, it is suitable for the temperature increase rate in a drying process to be 30 to 350 degree-C / sec. By firing the piezoelectric film 74 at such a temperature rising rate using the solution method, the piezoelectric layer 70 that is not pseudo-cubic can be realized. The “temperature increase rate” here defines the rate of time change of temperature from 350 ° C. until the target firing temperature is reached.

  Examples of the heating device used in the drying step, the degreasing step, and the firing step include an RTA (Rapid Thermal Annealing) device that heats by irradiation with an infrared lamp, a hot plate, and the like. The above process is repeated a plurality of times to form a first perovskite layer 171, a piezoelectric layer 70, and a second perovskite layer 172 composed of a plurality of composite oxide layers 173, piezoelectric films 74 and composite oxide layers 174. In the series of steps from the coating step to the firing step, the firing step may be performed after the coating step to the degreasing step are repeated a plurality of times.

  Further, before and after the formation of the second electrode 80 on the first perovskite layer 171, the piezoelectric layer 70, and the second perovskite layer 172, a reheating treatment (post-annealing) in a temperature range of 600 ° C. to 800 ° C. as necessary. May be performed. By performing post-annealing in this manner, a good interface between the first perovskite layer 171 and the second perovskite layer 172 and the first electrode or the second electrode 80 can be formed, and the first perovskite layer 171 and the piezoelectric layer can be formed. The crystallinity of the body layer 70 and the second perovskite layer 172 can be improved.

  In the present embodiment, the piezoelectric material contains an alkali metal (K or Na). Alkali metals are likely to diffuse into the first electrode 60 and the adhesion layer 56 in the firing step. If the alkali metal passes through the first electrode 60 and the adhesion layer 56 and reaches the wafer 110, it reacts with the wafer 110. However, in this embodiment, the insulator film 52 made of the above-described zirconium oxide performs a stopper function for K and Na. Therefore, it can suppress that an alkali metal reaches the wafer 110 which is a silicon substrate.

  Thereafter, the first perovskite layer 171, the piezoelectric layer 70, and the second perovskite layer 172 including the plurality of composite oxide layers 173, the piezoelectric film 74, and the composite oxide layer 174 are patterned to form a shape as shown in FIG. To. Patterning can be performed by dry etching such as reactive ion etching or ion milling, or wet etching using an etchant. Thereafter, the second electrode 80 is formed on the first perovskite layer 171, the piezoelectric layer 70 and the second perovskite layer 172. The second electrode 80 can be formed by the same method as the first electrode 60. Through the above steps, the piezoelectric element 300 including the first electrode 60, the first perovskite layer 171, the piezoelectric layer 70, the second perovskite layer 172, and the second electrode 80 is completed. In other words, the portion where the first electrode 60 and the first perovskite layer 171, the piezoelectric layer 70, the second perovskite layer 172 and the second electrode 80 overlap is the piezoelectric element 300.

  A layer or film formed by the solution method has an interface. Layers and films formed by the solution method leave traces of coating or baking, and such traces observe the cross section and analyze the concentration distribution of elements in the layer (or in the film). This is an “interface” that can be confirmed. Strictly speaking, the “interface” means the boundary between layers or films, but here, it means the vicinity of the boundary between layers or films. When a cross section of a layer or film formed by the solution method is observed with an electron microscope or the like, such an interface is near the boundary with the adjacent layer or film, or is darker than others, or more colored than others. Is confirmed as a thin part. In addition, when analyzing the concentration distribution of elements, such an interface is confirmed as a portion where the element concentration is higher than the other, or a portion where the element concentration is lower than the other, in the vicinity of the boundary with the adjacent layer or film. Is done. The piezoelectric layer 70 is formed by repeating a series of steps from the coating step to the baking step or by repeating the baking step after repeating the steps from the coating step to the degreasing step (a plurality of piezoelectric films). Therefore, it has a plurality of interfaces corresponding to each piezoelectric film.

  Next, as shown in FIG. 9, a protective substrate wafer 130 is bonded to the surface of the wafer 110 on the piezoelectric element 300 side via an adhesive 35 (see FIG. 4). Thereafter, the surface of the protective substrate wafer 130 is cut and thinned. Further, the manifold portion 32 and the through hole 33 (see FIG. 4) are formed in the protective substrate wafer 130. Next, as shown in FIG. 10, a mask film 53 is formed on the surface of the wafer 110 opposite to the piezoelectric element 300, and this is patterned into a predetermined shape. Then, as shown in FIG. 11, anisotropic etching (wet etching) using an alkaline solution such as KOH is performed on the wafer 110 through the mask film 53. Thereby, in addition to the pressure generation chambers 12 corresponding to the individual piezoelectric elements 300, the ink supply path 13, the communication path 14, and the communication portion 15 (see FIG. 4) are formed.

  Next, unnecessary portions of the outer peripheral edge portions of the wafer 110 and the protective substrate wafer 130 are cut and removed by dicing or the like. Further, the nozzle plate 20 is bonded to the surface of the wafer 110 opposite to the piezoelectric element 300 (see FIG. 4). Further, the compliance substrate 40 is bonded to the protective substrate wafer 130 (see FIG. 4). Through the steps so far, a chip assembly of the ink jet recording head 1 is completed. The ink jet recording head 1 is obtained by dividing the aggregate into individual chips.

Examples of the present invention will be described below.
Example 1
An elastic film 51 made of silicon dioxide was formed on the silicon substrate by thermally oxidizing the surface of a 6-inch silicon substrate that becomes the flow path forming substrate 10. Next, a zirconium film was formed on the elastic film 51 by sputtering, and the zirconium film was thermally oxidized to form an insulator film 52 made of zirconium oxide. Next, titanium was formed on the insulator film 52 by a sputtering method and thermally oxidized to form an adhesion layer 56 made of titanium oxide. Then, after depositing a platinum film on the adhesion layer 56 by a sputtering method, the first electrode 60 having a thickness of 50 nm was formed by patterning into a predetermined shape.

Next, the first perovskite layer 171 was formed by the following procedure. First, bismuth 2-ethylhexanoate, formulated to be BiFeO ₃ with a precursor solution comprising iron 2-ethylhexanoate, it was applied on the layer by a spin coating method (coating process). Then, drying (drying process) was performed at 180 ° C. and degreasing (degreasing process) was performed at 380 ° C., and heat treatment was performed at 550 ° C. using RTA (Rapid Thermal Annealing) (firing process). As a result, a BFO-based first perovskite layer 171 having a film thickness of about 30 nm was produced.

Next, the piezoelectric layer 70 was formed by the following procedure. First, using a solution composed of potassium 2-ethylhexanoate, sodium 2-ethylhexanoate, niobium 2-ethylhexanoate, manganese 2-ethylhexanoate (K _0.4 Na _0.6 ) (Nb _0.995 Mn _0.005 ) O ₃ was prepared and applied onto the layer by a spin coating method (application process). Then, it dried at 180 degreeC on the hotplate (drying process), and degreased (degreasing process) at 380 degreeC, and heat-processed at 700 degreeC using the RTA (Rapid Thermal Annealing) apparatus (baking process). And the process from a coating process to a baking process was repeated 7 times. Thus, a KNN-based piezoelectric layer 70 having a film thickness of about 550 nm was produced.

  Next, a BFO-based second perovskite layer 172 having a film thickness of about 30 nm was produced in the same procedure as the first perovskite layer 171.

  A second electrode 80 having a thickness of 50 nm was formed by forming a film of platinum on the second perovskite layer 172 by sputtering while heating at 200 ° C.

  Thereafter, in order to improve the adhesion between platinum and the second perovskite layer 172, the piezoelectric element of Example 1 was formed by performing reheating (post-annealing) at 650 ° C. for 3 minutes using an RTA apparatus.

(Example 2)
The same procedure as in Example 1 was performed except that an orientation control layer made of Bi (Fe _0.5 Ti _0.5 ) O ₃ was provided on the base layer of the first perovskite layer 171.

(Comparative Example 1)
The same procedure as in Example 1 was performed except that the first perovskite layer 171 and the second perovskite layer 172 were not provided.

  The following tests were conducted for each of the above-described examples and comparative examples. The results are shown in Table 1 and FIGS.

<Hysteresis measurement>
The PE hysteresis of the ceramic films of Example 1 and Comparative Example 1 was measured at a frequency of 1 kHz using “FCE-1A” manufactured by Toyo Corporation. The results are shown in FIGS. Although Example 1 shown in FIG. 12 has high insulation and shows excellent hysteresis, it was found that Comparative Example 1 shown in FIG. 13 has poor insulation and leaks.

<XRD measurement>
“D8 Discover” manufactured by Bruker AXS was used. Cu-Kα was used as a radiation source, and a two-dimensional detector (GAADDS) was used as a detector, and measurement was performed at room temperature. The results of Examples 1 and 2 are shown in FIGS. As a result, as shown in FIG. 14, in the piezoelectric layer of Example 1, the peak of (100) plane orientation of perovskite is observed when 2θ is around 22-23 °, and the (100) plane is preferentially oriented. I understood it. The same was true for Comparative Example 1.

  Further, as shown in FIG. 15, the piezoelectric layer of Example 2 is also preferentially oriented in the (100) plane, and it is confirmed that the peak of the (100) plane orientation of the perovskite is stronger than that in Example 1. It was.

(Test results)
From FIG. 12 to FIG. 15 and the results of Table 1, Examples 1 and 2 having a structure in which a piezoelectric layer is sandwiched between a BFO-based first perovskite layer and a second perovskite layer are the first perovskite layer and the second perovskite layer. It was found that the insulating property is high and the leak characteristics are good as compared with Comparative Example 1 in which no is provided.

(Other embodiments)
The embodiments of the piezoelectric material and the piezoelectric element of the present invention and the liquid ejecting head and the liquid ejecting apparatus on which the piezoelectric element is mounted have been described above, but the basic configuration of the present invention is not limited to the above. Absent. For example, in Embodiment 1 described above, a silicon substrate is exemplified as the flow path forming substrate 10, but the present invention is not limited thereto, and for example, a material such as an SOI substrate or glass may be used.

  In the first embodiment, the ink jet recording head has been described as an example of the liquid ejecting head. However, the present invention is widely applicable to all liquid ejecting heads, and is also applicable to a liquid ejecting head that ejects liquid other than ink. Of course, it can be applied. Other liquid ejecting heads include, for example, various recording heads used in image recording apparatuses such as printers, color material ejecting heads used in the manufacture of color filters such as liquid crystal displays, organic EL displays, and FEDs (field emission displays). There are electrode material ejection heads used for electrode formation, bio-organic matter ejection heads used for biochip production, and the like.

  The present invention is not limited to the piezoelectric element mounted on the liquid ejecting head, and can also be applied to a piezoelectric element mounted on another piezoelectric element application device. Examples of the piezoelectric element applied device include an ultrasonic device, a motor, a pressure sensor, a pyroelectric element, and a ferroelectric element. Further, a completed body using these piezoelectric element application devices, for example, a liquid ejection device using the liquid ejection head, an ultrasonic sensor using the ultrasonic device, a robot using the motor as a drive source, An IR sensor using the pyroelectric element and a ferroelectric memory using a ferroelectric element are also included in the piezoelectric element application device.

  In the description of the present invention, the components shown in the drawings, that is, the thickness, width, relative positional relationship, and the like of the layers may be exaggerated. Further, the term “upper” in the present specification does not limit that the positional relationship between the constituent elements is “directly above”. For example, the expressions “first electrode on the substrate” and “piezoelectric layer on the first electrode” may include other configurations between the substrate and the first electrode or between the first electrode and the piezoelectric layer. Do not exclude things that contain elements.

  DESCRIPTION OF SYMBOLS I ... Inkjet recording apparatus (liquid ejecting apparatus), II ... Inkjet recording head unit (head unit), 1 ... Inkjet recording head (liquid ejecting head), 10 ... Flow path forming substrate, 12 ... Pressure generating chamber, 13 DESCRIPTION OF SYMBOLS Ink supply path, 14 ... Communication path, 15 ... Communication part, 20 ... Nozzle plate, 21 ... Nozzle opening, 30 ... Protection board, 31 ... Piezoelectric element holding part, 32 ... Manifold part, 40 ... Compliance board, 50 ... Vibration Plate 51: Elastic film 52 ... Insulator film 56 ... Adhesion layer 60 ... First electrode 70 ... Piezoelectric layer 74: Piezoelectric film 80 ... Second electrode 90 ... Lead electrode 100 ... Manifold , 110 ... silicon substrate (wafer), 130 ... protective substrate wafer, 171 ... first perovskite layer, 172 ... second perovskite layer, 300 ... piezoelectric Child

Claims (10)

A first electrode;
A second electrode;
A piezoelectric layer made of a perovskite oxide including at least one selected from the group consisting of potassium, sodium, and bismuth and niobium provided between the first electrode and the second electrode;
A piezoelectric element comprising:
A first perovskite layer made of a perovskite oxide having a composition different from that of the piezoelectric layer provided between the piezoelectric layer and the first electrode side; the piezoelectric layer and the second electrode side; And a second perovskite layer made of a perovskite oxide having a composition different from that of the piezoelectric layer.   2. The piezoelectric element according to claim 1, wherein the first perovskite layer and the second perovskite layer include at least one selected from the group consisting of bismuth and iron.   The piezoelectric element according to claim 1, wherein the piezoelectric layer is preferentially oriented in a (100) plane.   4. The piezoelectric element according to claim 1, wherein the first perovskite layer is made of a perovskite oxide containing bismuth or iron and is preferentially oriented in a (100) plane.   5. The piezoelectric element according to claim 4, wherein an orientation control layer is provided between the first electrode and the first perovskite layer or between the first perovskite layer and the piezoelectric layer. .   6. The piezoelectric element according to claim 1, wherein the second perovskite layer is made of a perovskite oxide containing bismuth or iron, and is preferentially oriented in a (100) plane.   The piezoelectric element according to claim 1, wherein each of the first perovskite layer and the second perovskite layer is thinner than the piezoelectric layer.   The piezoelectric element according to claim 1, wherein the first electrode and the second electrode are selected from at least one material selected from Pt, Ir, and oxides thereof. .   The piezoelectric element according to any one of claims 1 to 8, further comprising a layer made of zirconium or zirconium oxide between the substrate on which the first electrode is provided and the first electrode.   A piezoelectric element application device comprising the piezoelectric element according to claim 1.

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